Currently, because a frequency division duplex (FDD) technology can support a transmitter and a receiver in separately working on different bands, the FDD technology is widely applied to various wireless communications devices. However, in a communications device using the FDD technology, a transmit (TX) signal is leaked to a receiving channel on which a receiver is located. A non-linear characteristic of each device in the receiver results in second-order intermodulation distortion (IMD2) interference. Such interference is typical self-interference.
As shown in FIG. 1, in an antenna diversity receiver, a main channel usually includes a main receiving channel (11→21→30) and a main transmission channel (30→22→21→11) that include a main antenna 11, an antenna diplexer 21, a power amplifier 22, and a mixer circuit integrated into a transceiver 30. A transmit signal transmitted on the main transmission channel (30→22→21→11) is leaked to the main receiving channel (11→21→30). To avoid interference caused by signal leakage of the main transmission channel to the main receiving channel (11→21→30), a common solution is performing second-order intermodulation intercept point (IP2) calibration on a main channel in a manufacturing line, to avoid IMD2 interference from the main transmission channel to the main receiving channel. However, for a diversity channel including a diversity antenna 12, a filter 23, and the mixer circuit integrated into the transceiver 30, the diversity channel is configured only to receive a signal but not to transmit a signal. Therefore, IP2 calibration cannot be performed in a wired environment. A common practice is using a default IP2 calibration code word to perform IP2 calibration, or directly using an IP2 calibration code word used when IP2 calibration is performed on the main channel. In addition, a surface acoustic wave (SAW) filter with a relatively high suppression degree and a fixed frequency needs to be used in the diversity channel to suppress signal leakage. In this calibration method, receive performance of the diversity channel of the diversity receiver cannot meet a requirement. In addition, this method goes against a high requirement of a mobile terminal that supports multiband receiving for a miniaturized and low-cost radio frequency subsystem.